1. Field of the Invention
This invention relates to pipeline inspection tools, and more particularly to apparatus and methods for a canister for use within an in-line inspection tool.
2. Background of the Invention
Oil, petroleum products, natural gas, hazardous liquids, and the like are often transported using pipelines. The majority of these pipelines are constructed from steel pipe. Once installed, a pipeline will inevitably corrode or otherwise degrade. Proper pipeline management requires identification, monitoring, and repair of defects and vulnerabilities of the pipeline. For example, information collected about the condition of a pipeline may be used to determine safe operating pressures, facilitate repair, schedule replacement, and the like.
Typical defects of a pipeline may include corrosion, gouges, dents, and the like. Corrosion may cause pitting or general wall loss, thereby lowering the maximum operating pressure of the pipeline. Vulnerabilities may also include dents, curvature and bending anomalies, and combined stress and chemical or biological action such as stress corrosion cracking. Without detection and preemptive action, all such defects and vulnerabilities may lead to pipeline failure.
Information on the condition of a pipeline is often collected using an in-line inspection tool. An in-line inspection tool typically uses sensors to collect information about a pipeline as it travels therethrough. In the past, in-line inspection tools have used magnetic flux leakage to determine the condition of a pipeline wall. Flaws in ferromagnetic pipe can be detected by the perturbations they cause in a magnetic field applied to the wall of a pipeline.
The sensors of an in-line inspection tool may generate signals characterizing the perturbations of the magnetic field. These signals (or derivatives thereof) may be stored on a memory device forming part of the in-line inspection tool. Accordingly, in-line inspection tools typically include computer hardware, power sources, and the like housed in canisters. Canisters typically perform two functions. First, they protect their contents from the environment within the pipeline. Second, they form the backbone of the in-line inspection tool.
Typical canisters have flanges extending radially therefrom. These flanges provide a location for bolting a canister to neighboring components such as driving cups, couplers, sealing surfaces or lids, other canisters, and the like. They also consume valuable space. That is, regardless of whether a flange extends radially inward or radially outward from a canister, anything inserted within that canister must be small enough to pass within the bolt circle of the flange. Thus, the flange limits the available internal space.
During the forty years that canisters have been used on in-line inspection tools, there has been a continual need for more interior space than can be accommodated by flanged canisters. Improved designs have expanded the interior of certain canisters by utilizing blind, threaded holes in flanges formed integrally with corresponding canisters. However, in such designs, the flanges continue to limit the diameter of the contents that can be admitted therewith.
As a central, structural component of typical in-line inspection tools, flanged canisters have been too important and performed too many functions to make a replacement evident. However, what is needed is a canister to house and protect components and provide the structural benefits of a flanged canister without the space-consuming liabilities thereof.